update offhours tag restrictions

[connorSanderson]

Update escape characters to allow the hyphen character to be escaped for resources which do not allow it as a tag value. For example, ecs services' tags.

[linux-foundation-easycla]

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• ✅ login: connorSanderson (c08e0e8)
• ✅ login: kentnsw / name: Kent Ou (9ade130, a917200)

[kapilt]

if this is ecs specific it feels like should handle it specific to that type, rather than force the default for resources where it is compatible. although its not clear if we do that with rds and others, tbd.

[kentnsw]

@connorSanderson @kapilt

Just want to add my understanding here. The "escape" feature in c7n is "decode" only, no "encode". It is to "decode" those escaped characters in tag value back to normal, eg, from u28 to (.

If the ( is supported by the tag value, user does not have to escape it, eg, in EC2 tag value, we can use normal string like off=(M-F,19);on=(M-F,7). But when comes to RDS, user has to "encode" ( to u28 to adapt to the restriction.

So IMHO, this PR looks good.

[kapilt]

thanks @kentnsw for the explanation

[kapilt]

lgtm